When the EGR valve pintle is stuck in the open position, it's usually caused by a build up of carbon and can be remedied by removing the valve and using carburetor cleaner and a pipe cleaner to clean it out. This works for IACVs too.
So that totals a cost of what? 3 bucks for carburetor cleaner? Saves you over $500, and you get a minor introduction to how satisfying (and cheap) it is to work on your car yourself. Buy a Haynes manual, they're indispensible.